1. Field of the Invention
The present invention relates to an electronic device including therein a Helmholtz silencer, and in more detail, to an image forming apparatus such as a copying machine, a facsimile, a printer, and a multifunction peripheral thereof.
2. Description of the Related Art
Recently, in an image forming apparatus, noise reduction and unpleasant sound reduction of machines have been demanded. In particular, such reduction is accelerating regarding a polygon motor of a writing unit that causes high-frequency unpleasant sound.
Japanese Patent Application Laid-open No. 2000-235396 discloses an invention in which a Helmholtz silencer is configured with an exterior cover so as to reduce noise of a device while saving space. However, the invention has the problem that it is difficult to design a desired distance between a noise source and a Helmholtz silencer and the problem that the costs are increased because the exterior cover is arranged on the entire side surface, for example.
That is, in the case of the conventional Helmholtz silencer attached to the exterior cover or the like, the Helmholtz silencer is separated from a writing unit (noise source), and thus the silencing effect is reduced. Furthermore, there occurs a problem of high-frequency unpleasant noise generated when a polygon motor of a writing unit rotates individually during operation.
When the Helmholtz silencer is arranged in the entire periphery of a noise source to prevent high-frequency noise from leaking to the outside in order to solve the problems, the costs are increased and the space cannot be secured.
When a target frequency is determined, the approximate size of a Helmholtz silencer is determined. Thus, when an installation position, a noise source, and a frequency are determined, a distance between the noise source and the Helmholtz silencer is determined to some degree. This causes a restriction that the noise source and the Helmholtz silencer cannot be brought closer to each other, thus reducing the silencing effect.
Moreover, in an image forming apparatus having a plurality of line velocities, a low frequency to a high frequency cause unpleasant noise, which is a problem. The inventors of the present application are not responsible for the conventional techniques for solving such a problem using a Helmholtz silencer.
Moreover, when the Helmholtz silencer is attached to an exterior cover of an image forming apparatus body, the cover opening or closing operation force is increased, causing a problem of the obstacle to the operation of inserting or taking out inner units. When the Helmholtz silencer is configured integrally with the exterior cover, the cover needs to be formed newly when used in a similar model with a slight difference.
In view of the conventional problems, there is a need to improve the arrangement of the Helmholtz silencer and the silencing effect thereof.